Air Bubbles Under Fondant aka Cake Farts

Recently in London the weather has been warming up (shock horror!) which has been causing havoc with some of my cake making. Those of you who work regularly with rolled fondant (called sugarpaste here in the UK) and buttercream know that heat can be your worst enemy when it comes to cake decorating.

Our flat, in typical London fashion, has heating but no air conditioning. The kitchen is near the back of the apartment, as far away from the windows as you can get. So on a warm day, it’s like an oven in the kitchen, somewhat ironically. One of the tricks I use when it’s warm and my buttercream is melting is to put my cake in the freezer once it has the crumb coat on. Just for a little while to let the buttercream get nice and stiff so it doesn’t move around when I put the rolled fondant on it. This usually works really well and helps me achieve a nice smooth covering on the cake.

However, using this method in the heat has meant that recently I have been getting small air bubbles on some of my cakes. This is unusual for me, but not a big deal as I can usually smooth them out without too much difficulty. But then of course, there was the one time this week when it was an absolute disaster!

I made a cake and left it in the freezer for far too long – about 40 minutes! When I covered it with fondant, everything seemed fine. I got a nice smooth covering on the cake and left it to dry. I came back an hour later and found a small air bubble under the rolled fondant. Not a big deal, I smoothed it out and transferred the cake to the fondant covered cake board, cementing it securely to the board. I left it for a half hour then went to put some ribbon around the cake while the icing was still slightly wet. And I nearly fainted when I saw it!

There was not one, but two HUGE air bubbles under my fondant!!! Mice could have crawled under there and set up camp they were so big! (Please note: I do NOT have any mice in my flat). It was a deformed, bubbly mess. The back of the cake reminded me of a witch’s hooked, crooked nose, and the top of the cake looked like the elephant man. It looked like something that belonged on the Cake Wrecks blog!

I have covered quite a few cakes with fondant in my time and NEVER had this happen before. Which prompts me now to explain how it did happen this time. When you cover a cold cake with fondant, small pockets of air are released as the cake warms up and returns to room temperature. This causes a bubble of air to be trapped under the fondant. It’s what we call in the biz a “cake fart” as the cake is releasing gases! This had been happening a little with my cakes recently due to them being put in the freezer then taken out into a very warm room. A small air bubble is no biggy, but if you have a very cold cake in a very warm room, your air bubbles will be particularly bad and ginormous. Which is what happened in this situation as I’d left the cake in the freezer too long!

So how did I fix the problem? Removing the fondant and re-covering is really a very last resort, especially when you’ve already fixed the cake onto the covered board. So what I do is sterilise a very thin pin or needle, then poke a small hole into the air bubble at an angle. I then get my cake smoothers and push the air out of the offending bubble, then smooth over the area with the paddles. If the hole is very noticeable, you can cover it with decoration such as a flower or ribbon, but if it’s somewhere on the cake that isn’t going to get covered with decoration, you can also mix a small amount of rolled fondant with water and fill the hole in, then smooth with your smoothing paddles. And voila, it’s like your air bubble never existed!

I don’t have any pictures of the cake fart disaster to show you as I was in such a panic at the time that I didn’t even think to grab my camera and document the moment. But here are some pics of another cake which had an air bubble which I fixed with the pin method:

Before – you can clearly see an air bubble has formed around the wooden post

After – air bubble, what air bubble?

UPDATED 2016: This is by far my most popular post! I’ve noticed that some of you are confused between cake farts and normal air bubbles. The cake fart is different to a normal air bubble, it’s caused by a dramatic enough difference in temperature between the fridge/freezer and the room temperature and it usually forms some time after you’ve covered your cake if you covered a cold cake. So you’ll cover your cake perfectly and come back later to find HUGE air bubbles that weren’t there before.

Many cake makers cover cakes straight from the fridge or freezer with no problems because the room they take the cake out into from the fridge/freezer isn’t too hot. I usually can’t because it’s so hot and humid in Australia and I don’t have a temperature controlled room (no air con, it’s brutal!). I use ganache instead of buttercream now and always cover a room temp cake so cake farts are a thing of the past.

Normal air bubbles form straight away as you cover your cake. I get these either because I missed a spot when wetting my ganache before covering the cake or the fondant didn’t quite stick down to the surface in a spot when covering the cake, these air bubbles are usually quite small (cake farts can be humungazoid). I don’t know any cake decorator that doesn’t get these kind of air bubbles, but they’re easily taken care of with the pin trick as soon as you cover your cake. Air bubbles are all but impossible to get rid of once your fondant has set hard.

26 Responses to “Air Bubbles Under Fondant aka Cake Farts”

I call those “tumors”, that’s funny. You really have to make sure that you press all of the air out of the cake, especially if you have a layer cake with a filling in the center, before you cover it. It can happen with buttercream icing, too, unfortunately.

I laughed and cried when I read your post. This exact same thing happened to me – except I’m in Australia and we had a dry warm wind blowing the day I made my cake and didnt realise the front door was open and my massive air bubble (right in the middle center) had formed and set hard because of the wind!!!!! I nearly died – I did pop it but the icing was wrinkled and looked horrible! I didnt have time to make another so that is where we placed the candles…. over my major opppppsss! 🙁 It ended up coming out ok in photos – so I was happy!

Oh my god!! I have a total cake disaster… and this is what you are describing! I have recently learnt at Planet Cake in Australia how to cover a ganached cake in fondant. During my 2 weeks there i did really well.. only to come back and have what you described happen to me twice!!!! Not once twice.. i cried so much as i did so well in Australia. I live in Singapore so we are in constant humidity.. i store all my chocolate covered ganaced cakes in our wine fridge.. and yesterday i made a perfectly lovely fondant covered cake with quilting around the sides.. and when i went back to it 2 hours later there was that air bubble cracked and looked like the cake was emitting gas!! I can’t do the fix you say as my cake has quilting on the side. this is another cake i shall be giving away.. but i am going to do another for practice and leave it sitting out of the wine fridge for at least 1/2 and hour before i cover it in fondant i will send a picture of what has happened and please let me know if this is same as you have experienced… it sounds like it 🙁

This has been happening to me A LOT lately. And it’s incredibly discouraging as a cake decorator. I’ve done a lot of research to determine what I was doing wrong. And now I am very careful to make sure there are no air bubbles in my buttercream before covering with fondant, and making sure the fondant is good and smoothed out on top of the cake before working down the sides. But it STILL continues to happen. It never dawned on me that the refrigerator could be causing this problem. I usually ice the cake and then place it in the fridge for a while to set. Should I let it set out on the counter instead of the refrigerator before covering? And is it okay to place in the fridge once I’ve covered, or will there still be the threat of a cake fart once I remove? Thanks for the advice!

Hi Rachel,
I often put my cake in the fridge or freezer to set my ganache, but I make sure it returns to room temp before I put the fondant on. With buttercream, I stick it in the freezer to set for around 8 minutes, never any longer than 10 minutes, and make sure the room is cool before taking it out of the freezer and putting the fondant on. If you are using a crusting buttercream, then I’d wait for it to return to room temp before covering with fondant OR let it set on the counter. Some of the buttercreams I use do not crust so I have to cover them as soon as they come out of the freezer while the buttercream is still hard, which is when it’s important not to let the cake sit in the fridge or freezer too long and to make sure the temperature in the room is reasonably cool.
I never put fondant covered cakes in the fridge myself, I find it causes the fondant to sweat, but I have heard of other cake decorators putting them in the fridge without any problems. Just make sure the room is not too warm when taking it out of the fridge.
Thanks for reading!
Charmayne from Delicious Cake Design

I live in South Africa and I’ve been having the same problem for the past few weeks, and it has never happened to me before. I’ve been baking cakes for the last 5 years and this has become very discouraging, to say the least. I thought I was losing my “touch”. I’ll definitely only put the cake in the fridge to setup and let it come back to room temperature before I cover it with fondant. Thanks for the great tip!

OMG this has happened to me today. Huge bubble formed on my perfect cake. I did the pin thing but was not happy so today ripped off the fondant fixed the ganache and redid cake. Had it under air conditioner on dry for a couple of hours and as soon as I turned it off another bubble appeared. This time I put a huge hole under a decoration and put a hole in the centre of cake under topper. I keep checking it now as it is being picked up in an hour I will just die if it happens again. At least I now know why. I left cake in fridge overnight covered in ganache. Thanks for the explanation I too thought I was losing my touch.

Sadly fridge won’t fix it. I make 100s of cakes a year. Last night a huge bubble formed and destroyed a cake in the cooler. Normally only a curse out of cooler…. always seems to happen when its humid. my dehumidifier broke…every single cake (8 of them) bubbled. disaster. forbuear we have frosted cakes cool from fridge…have had a bubble in a year. Dehumidifier breaks, every cake ruined. Even those in cooler

I thought my bubbles were due to my inexperience. Couldn’t understand why some cakes were fine and other where inexplained disasters. This has she so much light on such a frustrating outcome. Christen I had a similar disaster in that air bubble formed hours before client was due to pick it up. So so so stressful, nearly stopped decorating after this, but I’m back on track and the information here has shed so much light. Thank you thank you

Sweet baby Jesus! I too had this problem today. Mine wasn’t fixable so I had to improvise. It was the most stressful 3 hrs… I never had this happen to me before… Now I know I didn’t let it thaw out completely. And I kept putting the cakes in the freezer after I would,crumb them… I feel super awful about this cake to the point I wanna give my customer a refund and quit baking cakes! Thanks doll! I know what I did wrong and I will learn from this!

Please help!! I keep getting air bubbles between the cake and the ganache, I have no idea what I am doing wrong, last night I left my cake out after it had been chilled and a big bubble formed before I even had a chance to put any fondant on, do you have any suggestions as to what I’m doing wrong? this is the third time its happened and its so stressful. Thanks

Oooh, Caroline, you have me stumped! I haven’t ever had this problem, my air bubbles always form between the ganache and the fondant, not the cake and the ganache. I chill my cakes after ganaching for about 20 minutes before I smooth it with a warmed metal scraper then I leave it out at room temp overnight to set. I have on occasion left them in the fridge for up to 3 or 4 hours but I’ve never had this problem. How long are you chilling them for? Could you be chilling them too long? Maybe it’s a problem with your ganache. What ratio of chocolate to cream are you using in your ganache and what type of chocolate and cream? Are you letting the ganache set overnight before using it?

I know this is somewhat late but just stumbled upon this page. When you have ganached your cake use a scewer or dowel to push a hole stright through the centre. This will allow any air in your cake or ganache to escape and your ganache will still set fine
Cover this hole up before covering with fondant. I offen redo the hole after fondant to prevent air bubbles. Hope that helps
Sophie

Thanks for getting back to me, I use 300ml double cream and 600g milk chocolate and I always leave it out to set overnight before using it. Once my cake is covered I then leave the cake in the fridge overnight BEFORE covering with fondant. I find that when I don’t leave it in the fridge it doesn’t seem to form a hard enough shell especially in hot weather. I also always put my fondant covered cakes in the fridge but will stop doing this. Maybe I am using poor quality chocolate as sometimes I use cake covering chocolate .

Hi! I have not been having this issue at home that often and i sometimes chill them sometimes not (mostly not) but at work it happens alot and they are huge bubbles! I made a car cake at work on a wednesday and it was fine all of thursday then on friday morning came in to a massive airbubble under the sugarpaste on the side of the car, the fondant had stretched and i could do nothing about it!! The cake was sat on a work top with a fridge under it, normally no issue would happen but our buttercream at work uses icing sugar with corn flour in and im wondering if the slight heat from the fridge, or even just in the room, is causing it to ferment and air bubbles to grow. my colleagues theory was that the slight heat from the fridge unit could have caused the sugarpaste to soften allowing the bubble to grow but i am concerned about it reoccuring. I am tempted to bring it up with the bakery, either persuade them to have ganache around the sides or a buttercream without corn flour. Any thoughts on this?

This post as been awhile now but but reading it, I think it’s not really the fridge that makes the car bubble out. I’ve made many cakes in the past and have only had this issue on occasions were I’m short of time and last minute. I think its when I haven’t fully covered all areas between filling and the crumb coat. Any left gaps not filled before covering the cake will have these bubbles form regardless the freezing time. I just need to be more careful when filling and crumb coating and doing the final later of buttercream or ganache properly and not to miss a spot before doing fondant over. Having said this, to make sure it doesn’t happen, I simply take a dowel/skewer or straw and poke a hole at the top in the centre of any and every layer of cake I’m covering for fondant and I’ve ne’er had the problem again. This gives the air a way out while firming up and drying/hardening. It helps, do try it.

Oh thank you thank you thank you. I’ve been making cakes for forty years but only just started having this ‘cake fart’ issue. Today, my beautiful blue fondant 6″ high cake developed a tumour the size of London…and I’ve wrecked the thing trying to release the trapped air!!! Hopefully, the massive amount of decoration pieces will cover the damage adequately (it’s for a3yr old) and the front seems ok..so far (!) But the main thing is- I’ve learnt a new thing!!!! NO gaps, and NO fridge. I only started putting my cakes in the fridge or freezer because a very nice professional lady online.. No names.. said it was essential and I found it worked quite well. But back to the drawing board I guess.
Thank you again.

Mega thanks for your reply! This was a gluten free cake (i only do gf cakes), advice is to tort, ice and crumbcoat while the cakes are either well chilled or better still frozen as this helps prevent the inherent crumbling of gf cakage. I’ve done it SOoo many times and never had much of an issue…but yesterday. Well. Nightmare. The cakes were frozen and I iced them, chilled and then fondanted as usual. Kitchen must have been warmer than I thought. An hour later…I was crying.
It’s devastating to see one half of a beautifully iced cake with the fondant stretched WAY beyond repair. I had to cut a section out, put this at the back and patch it. The finished cake looks totally fine…but I took pictures before I disguised it just to remind myself.
I’m so grateful for this blog. I had NO IDEA what I’d done…! Now I understand and will never make the same mistake again! Gluten free cakes may be slightly more difficult to work with, but from now on- no shortcuts. And no freezer.
Keep up the sterling work. Your cakes are totally superb!
All the best from Blighty x

Thanks for this post! I’ve been decorating cakes for 6/7 years and I’ve only ever had the odd small “cake fart” but recently this has happened numerous times and it’s been driving me nutty! I put it down to the heat and humidity but it is cooler now and yet this morning I woke up to a giant cake fart on a cake. Luckily it seems fixable. My other cake (iced etc last night using the same method) seems to be fine! I do usually fridge my cakes to allow the buttercream coating to set nicely ready for covering in sugarpaste – this has always worked a treat so I’m baffled that this is suddenly happening however I can only put it down to the fridge/atmosphere/Temperature difference?? I’ve also noticed that the sugarpaste starts to go sticky rather than setting hard and the buttercream underneath is soft whic makes it really hard to use the smoothers as they stick! Has anybody else had this particular problem?

This is so funny !! … And Im glad Im not the only one with cake fart disasters, as there have been a few for me too and I welcome the ideas on why this happens, as it has been baffling me for a long time.

I do use the pin trick, which does come in handy during panic time!! .. But I hate it when the bubbles do not decide to turn up until your about to wheel it out of the door 😮

Happened this last Saturday to me for the first time! Unfortunately it appeared right before the bride and groom went to cut the cake. It was an all white marshmallow fondant cake. Simple. And there it was, front and center…a 3+” bulge half way down the front. We couldn’t turn it around because of the sparkly trim seam that was in the back. So my cake fart aka the big white cake boob will forever be seen in the wedding photos. 😥😥😥. So happy the bride and groom have a great sense of humor!